1. Field of the Invention
The present invention relates to a rapid reel braking device deck mechanism of the video cassette tape recorder and adapted to rapidly stop the rotation of supply and take-up reels engaged with a reel of a tape cassette, when it is desired. More particularly, the present invention relates to a rapid reel braking device for a video cassette tape recorder, which can rapidly and accurately stop the rotation of supply and take-up reels when the operation of the recorder is changed from a FF/REW (Fast Forward/Rewind) mode to a stop mode.
2. Description of the Prior Art
Generally, a video cassette tape recorder operates in a various modes, such as FF, REW, PLAY, REV, and PAUSE modes. When the operation mode of the video cassette tape recorder is changed, many parts of the deck mechanism must be moved to desired positions thereof, respectively, in order to carry out their functions in the changed operation mode.
Conventionally, mechanisms of various arrangements have been proposed, in order to move parts of the deck mechanism depending upon the change of the operation mode thereof. For example, a button-type mechanism has been proposed, which includes several buttons having a shape of, for example, a piano keyboard and utilizes the displacement of each button caused by pushing the button. Recently, many deck mechanisms obtain such displacement by utilizing a cam having a cam groove of a predetermined shape.
Such cam is provided, at the peripheral surface thereof, with a gear, in order to receive a power from the outside. The cam also has at upper and lower surfaces thereof spiral cam grooves into which a pin protruded from a function plate is inserted. As the cam rotates, the function plate is operated by the engagement between the groove and the pin. Thus, various operation modes of the video cassette tape recorder can be carried out.
In the case when a desired operation mode, particularly, FF mode or REW mode, of the recorder is carried out by the operation of the function plate resulted from the rotation of the cam, the supply and take-up reels are rotated at a high rate. As a result, when the operation mode of the recorder is changed from such modes to the STOP mode, the supply and take-up reels are still rotated more or less, due to the rotational inertia thereof. Thereby, it is difficult to stop, at a desired position, the tape which is taken out of the cassette and wound on the rotating drum. Furthermore, since the tape is continuously taken out of the cassette, by the length corresponding to the rotation amount of the reel resulted from the rotational inertia thereof, the tape may get tangled and even damaged. Accordingly, it is necessary to provide a rapid reel braking device which can apply a sudden brake force to the supply and take-up reels, in order to eliminate the above mentioned problems.
Referring to FIG. 1, a rapid reel brake device which has been applied to conventional deck mechanism is shown.
In the drawing, reference numerals 1 and 2 designate a supply reel and a take-up reel of a deck nechanism, respectively, which are also referred to as a reel table or a reel stand. Reels of a tape cassette are fitted around the upper portions of the supply and take-up reels, respectively. Adjacent base plate of the supply and take-up reels, a pair of brakes 3 and 4 are pivotably mounted by means of pins 5 and 6, respectively. Each brake 3 (or 4) has a brake shoe 3a (or 4a) attached on one end of the brake adjacent the reel 1 (or 2). Brakes 3 and 4 are connected with each other, at the other ends thereof positioned away from the reels, by means of a spring 7. By the spring 7, each brake shoe 3a (or 4a) is biased against the peripheral surface of the reel 1 {or 2).
Each brake 3 (or 4) has at the middle portion thereof an elongated portion 3b (or 4b) extending toward the other brake 4 (or 3). The extension 3b of the brake 3 is provided at the free end thereof with a slot 3c. The extension 4b of the brake 4 is also provided at the free end thereof with a connecting pin 4c which is inserted into the slot 3c of the brake 3, in order to operatively connect brakes 3 and 4. Adjacent the other ends of the brakes, a function plate 9 is disposed. The function plate 9 has a pair of slots into each of which a guide pin 8 protruded from a base plate of the deck is inserted. The function plate 9 is guided to move laterally by the guide pins 8. The function plate 9 also has at one end thereof a function pin 9a protruded from the lower surface of the function plate 9.
Adjacent to the end of the function plate 9 provided with the function pin 9a, a cam gear 10 is disposed. The cam gear 10 has at the upper surface thereof a spiral cam groove 10a in which the function pin 9a of the function plate 9 is inserted. The cam gear 10 is engaged with a worm 12 connected to pulley 11a of a drive motor 11. By this arrangement, as the drive motor rotates, the rotational power is transmitted to the cam gear 10, via the pulley 11a and the worm 12. As the cam gear 10 rotates, therefore, the function plate 9 is moved laterally in one direction or the opposite direction, depending upon the change of the radius of the cam groove 10a at the position of the function pin 9a.
On the function plate 9, a slide plate 13 is disposed. The slide plate 13 also has a pair of slots to receive the guide pins 8 so that it can slide on the function plate 9. In addition, the slide plate 13 has at one end thereof an inclined surface 13a against which the protrusion 4d of the brake 4 can contact. To this end, the protrusion 4d of the brake 4 is more or less longer than that of the brake 3. To the other end of the slide plate 13, a spring 18 is mounted, which functions to bias the slide plate 13 away from the cam gear 10.
Adjacent the end of the slide plate 13 provided with the inclined surface 13a, an operating lever 14 is pivotably mounted by means of a pin 15., The lever 14 has at one end thereof a contact member 14a formed by bending upwardly the end of the lever 14 The lever 14 is subject to a clockwise pivoting force by the torsion spring 16 fitted around the pin 15.
The lever 14 is also provided, at the edge of the middle portion thereof, with a shoulder 14b which can engage with a protrusion 9b of the function plate 9 so that the slide movement of the slide plate 13 caused by the force of the spring 18 can be limited. In order to limit the clockwise pivoting of the operating lever 14, the function plate 9 has a protrusion 9c and the lever 14 has a protrusion 14c engageable with said protrusion 9c of the function plate 9.
Adjacent the brake 4 for the take-up reel, a solenoid 17 is fixedly mounted on the base plate of the deck. When an electric power is applied to the solenoid 17 via a certain circuit (not shown), the contact member 14a of the operating lever 14 is contacted to the solenoid 17, thereby causing the protrusion 14b of the lever 14 to be disengaged from the protrusion 9b of the function plate 9.
At the stop mode of such arrangement of the conventional rapid reel braking device, brakes 3 and 4 closely contact to reels 1 and 2, respectively, as shown by the dotted line in FIG. 1. The slide plate 13 also has been moved by a certain distance toward the left of FIG. 1 so that the protrusion 4d of the brake 4 for the take-up reel is separated from the inclined surface 13a of the slide plate 13. Under such condition, brakes 3 and 4 pivot toward reels, and 2, respectively, by the spring force of the spring 7, so that brake shoes 3a and 4a apply a braking pressure to peripheral edges of reels 1 and 2, respectively. As the cam gear 10 is rotated by a certain angle from the stop mode, by driving the motor 11, the position of the function pin 9a of the function plate 9 in the cam groove 10a of the cam gear 10 is varied such that the radius of the cam groove
of the function pin 9a is gradually increased. 10a at the position As a result, the function plate 9 is moved toward the right of FIG. 1, so that the slide plate 13 is moved together with the function plate 9 toward the right direction. The reason why the slide plate 13 can be moved together with the functon plate 9 is because the protrusion 14b of the operating lever 14 which is always subjected to the clockwise pivoting force by the torsion spring 16 is engaged with the protrusion 9b of the function plate 9, as above mentioned.
By such right movement of the slide plate 13, the inclined surface 13a of the slide plate 13 pushes the protrusion 4d of the brake 4 for the take-up reel 2, so as to pivot the brake 4 in the counterclockwise direction. Simultaneously, the brake 3 for the supply reel 1 is also pivoted in the clockwise direction, since the brake 3 is connected to the pin 4c of the brake 4. Thus, both brakes 3 and 4 are moved away from the supply and take-up reels 1 and 2, respectively, as shown in the solid line of FIG. 1. Accordingly, FF/REW or the play operation modes can be carried out.
When the operation mode is again converted from such modes into the stop mode, the function plate 9 is moved toward the left by the reversed rotation of the cam gear 10. Thereby, the slide plate 13 is also moved toward the left, so that the inclined surface 13a of the slide plate 13 disengaged from the protrusion 4d of the brake 4 for the take-up reel 2. As a result, brakes 3 and 4 pivot about pins 5 and 6 toward the supply and take-up reels and apply the braking forces thereon, respectively.
If a conversion command into the stop mode is input during the operation of FF/REW mode, the cam gear 10 reversely rotates and the function plate 9 moves toward the left, as in the above case. Simultaneously, a voltage is applied to the solenoid 17. Then, the supply of the voltage is instantly stopped. Accordingly, the contact member 14a of the operating lever 14 is contacted to and then instantly separated from the solenoid 17. At this time, the protrusion 14b of the operating lever 14 is disengaged from the protrusion 9b of the function plate 9. Simultaneously, the slide plate 13 is urged toward the left by the spring 18, so that the inclined surface 13a disengaged from the protrusion 4a of the brake 4 for the take-up reel 2. Thus, both brake shoes 3a and 4a of the brakes 3 and 4 are rapidly contacted to the reels 1 and 2, respectively, so that both reels 1 and 2 are stopped at the same time.
After a sudden braking force is applied to both reels 1 and 2 by the left movement of the slide plate 13 due to the spring force of the spring 18, the cam gear 10 continuously rotates in the counterclockwise direction. As a result the position of the function pin 9a of the function plate 9 in the cam groove 10a of the cam gear 10 is varied such that the radius of the cam groove 10a at the position of the function pin 9a is gradually reduced. Thereby, the function plate 9 is moved toward the left by a certain distance, so that the protrusion 14b of the operating lever 14 is again engaged with the protrusion 9b of the function plate 9. At this state, when the operation of PLAY mode or FF/REW mode is required, 10 the function plate 9 is moved toward the right by the clockwise of the can gear 10. This, brakes 3 and 4 are moved away from the reels 1 and 2.
Such type of the conventional rapid reel braking device has a complicated overall construction, because in addition to the function plate 9, the slide plate 13 and the operating lever 14 are used. As a result, it is impossible for the device to be compact. Due to the use of expensive solenoid 17, it is necessary to provide a separate circuit for connecting and disconnecting the solenoid to and from an electric power source. As a result, there are problems of the increase of the consumption of the electric power, the increase of the manufacture cost.